Statistics on causes of death and rates of hospitalization and treatment in the world show that cerebrovascular diseases always rank high. In particular ischemic cerebrovascular diseases are recently increasing as compared with hemorrhagic cerebrovascular diseases. An ischemic cerebrovascular disease is choking of the cerebral blood flow by some causes, ultimately resulting in necrosis of the cerebral tissue. Inter alia, neuronal cells are vulnerable and therefore ready to die on occurrence of ischemia. Neuronal cell death due to ischemia is known to be the most common condition leading to falling off of nerves due to a cerebral disturbance (see Shinkei Shinpo, Vol. 36(2), pp. 225-235 (1992) and Dementia, Vol. 7, pp. 161-171 (1993). Hence, a substance which prevents neuronal cell death is believed to create a therapeutic and prophylactic agent effective on a cerebrovascular disease. However, such an agent having sufficient efficacy has not yet been found.
It is known that similar neuronal cell death also accompanies a traumatic head injury and postencephalitis (see J. Neurosurq., Vol. 67, pp. 110-119 (1987), Shinken Shinpo, Vol. 35(5), pp. 705-716 (1991), and Taisha, Vol. 26, pp. 253-257 (1989)). Accordingly, prevention of neuronal cell death is considered to be treatment and prevention effective on these diseases.
It is known that a 4-acylaminotetrahydrofuro2,3-b!quinoline derivative improves reduced high affinity choline uptake (see JP-A-3-218361, the term "JP-A" as used herein means an "unexamined published Japanese patent application"), but it is unknown that this compound is effective on neuronal cell death.
The inventors of the present invention have extensively studied in order to develop an effective drug on cerebrovascular diseases, traumatic head injuries, postencephalitis, etc. As a result they have found that a 4-acylaminotetrahydrofuro2,3-b!quinoline derivative and an acid addition salt thereof or a hydrate or a solvate of them have a protecting action against delayed neuronal cell death by cerebral ischemia and completed the present invention.